GB2074395A - Seals of cable cores to cable glands - Google Patents

Abstract

A cable core 30 is sealed to a gland 10 by means of a mass of curable or hardenable compound 37, a sleeve 31 and a core seal element 40. The compound 37 fills the space between the sleeve 31 and the core 30 and is sealed to the sleeve, and the core seal element 40 seals the core 30 to the compound 37. The element 40 ensures a fluid-tight seal between the compound 37 and the core 30 on curing of the compound. The element 40 may be an elastomeric tube or may be formed of natural rubber, synthetic rubber, neoprene, synthetic plastics or may comprise a layer of low viscosity curable epoxy resin or hard setting glue or a layer of wound metallic tape. The compound 37 may be a low shrinkage, two-part epoxy resin putty and is chosen to adhere to the sleeve material which is preferably metal and is roughened to improve adhesion. The core seal element 40 may take a variety of forms (see Figs. 6A to V, not shown). <IMAGE>

Description

SPECIFICATION Improvements in or relating to cable glands This invention relates to the sealing of cable cores and where appropriate any sheath around those cores to a cable gland or other fitting, in order to prevent gases or liquids which may be dangerous, from passing into the cable at a termination of the cable. The invention finds particular application in flameproof glands for cables where the gases may be combustion or explosion products.

When sheathed cables which do not have full moulded cores, and thus have spaces between the conductor elements and other structural elements and the cable sheath, are terminated, for instance in flameproof or waterproof glands, there is the possibility of communication through the gland and the spaces in the cable structure between a casing or other space to which the gland is attached and the exterior of the cable sheath, either through failure of the sheath in the case of a flameproof gland in an explosion, or through a leak in the sheath in the case of a waterproof gland.

Previously known techniques for meeting this problem have involved placing a specially adapted gland around the termination of the cable where the core is to be sealed to the sheath, and surrounding the end of the cable sheath and the individual conductors which may be protecting from the sheath at the termination with a hardenable or curable compound. The gland has been designed so that before the compound hardens or cures it can be subjected to pressure by tightening elements of the gland. The subjection to pressure has been necessary as the compounds used for sealing the cable core undergo a considerable shrinkage when they harden or cure and thus if they are not subjected to pressure do not adequately seal either to the cable core or to the gland body.Again the compounds have been highly viscous in their raw state, and the subjection to pressure has been necessary to ensure that the compound enters all the interstices in the structure of the cable.

These known techniques have required the use of a specially adapted gland whenever a cable core is to be so sealed.

It is therefore an object of the present invention to provide an arrangement which can be used to seal a cable core to a gland or other fitting with a compound without the need for such subjection to pressure. It is a further object of the invention to provide such an arrangement which can be used with conventional cable glands or fittings.

Accordingly the present invention provides an arrangement for sealing a cable core to a cable gland or other fitting, comprising a sleeve member arranged to be located and sealed in the cable gland or fitting with the cable core passing through the sleeve, a curable or hardenable compound filling disposed to seal the space around the core in the sleeve, and a seal element disposed around the core to seal the core to the compound filling.

The compound filling may preferably comprise a two-part epoxy putty which will adhere to the material of the sleeve member.

The sleeve member is preferably of metal and may be roughened internally to assist adhesion of the compound filling.

The seal element may take the form of a rubber, synthetic rubber or other elastomeric material ring-seal element, the form of a metal tape wound round the core with a contact adhesive between the tape and the core, and between the tape and the compound filling, or it may take the form of a layer of adhesive or glue which will adhere to the surface of the core and to the compound filling.

In order to promote a fuller understanding of the above and other aspects of the present invention, some embodiments will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows in schematic cross-section a cable gland embodying the invention, Figure 2 shows in schematic cross-section a second cable gland embodying the invention, Figure 3 shows in schematic cross-section a third cable gland embodying the invention, Figure 4 shows in schematic cross-section a fourth cable gland embodying the invention, Figure 5 shows in schematic cross-section a fifth cable gland embodying the invention, Figures 6a through to 6v show cross-sectional views of various core seals for use in the embodiments of Figs. 1 through to 5, Figures 7a through to 7d show various sleeve members for use in the embodiments of Fig. 1 through to Fig. 5, and Figure 8 shows a cross-sectional view of a sixth cable gland embodying the invention.

Fig. 1 shows a cable gland 10 for use in terminting a cable 11 at the point where it enters an enclosure, in a flameproof manner.

The cable gland comprises a body 1 2 which has a screw-threaded nose 1 3 by which it may be screwed into an aperture in an enclosure, or locked in an unthreaded aperture by means of a locking ring or nut in conventional manner per se. The gland 10 further comprises a body sleeve 14 which is screw-threaded into the body 12, in this embodiment by means of an internally and externally screw-threaded adaptor sleeve 15, and which at the outer end is formed with a conical seating 1 6 to provide gripping means for armouring wires or the like of the cable 11. An armour gripping sleeve 1 7 is screw-threaded onto the sleeve 14, being provided with an internal seating 1 8 to complete the armour wire gripping means in known manner per se.The sleeve 1 7 is also provided at its outer end with a cable sleeve sealing ring 1 9 which is distorted in the sleeve 1 7 onto the cable 11 by means of a screw-threaded ring 20 through the intermediary of a mouided plastics material slip ring 21.

Thus it can be seen that the cable gland provides for the termination of the cable 11 and the entry of the cores into an enclosure in which the body 1 2 is fitted. The parts of the cable gland so far described may be as described in this particular embodiment or if desired of more or less any suitable conventional design as long as they provide for the receipt and gripping of the cable 11 in a manner appropriate to the construction of that cable in a manner which is acceptable having regard to the flameproof or other requirements of the application.

In the embodiment of Fig. 1 a single cable core 30 is shown although it is to be understood that any number of cores appropriate to the overall size of the gland may be incorporated in glands embodying the invention.

A sleeve member 31 is provided as a fit in the core of the body 1 2 to provide a flame path 32 which meets with the approved criteria for such a flame path in a flameproof gland. A seal 33 which may be of neoprene or other suitable material is provided between the sleeve member 31 and the gland body 1 2. The body 1 2 includes a conical seat 34 against which the seal 33 is urged to distort it to seal on and grip the sleeve member 31, by means of the sleeve 14 being screwed into the body 12. A slip washer 35 preferably formed of synthetic plastics material, is interposed between the sleeve 14 and the seal 33 although in some embodiments this may be left out. Thus it can be seen that the sleeve member 31 may be sealed in and gripped in the gland body 12.In the embodiment shown in Fig. 1 the sleeve member 31 is formed with a shoulder 36 which abuts the inner end of the gland body 1 2 to resist outward movement of the sleeve member 31 under the influence of any fluid pressure which may arise in an enclosure to which the gland is fitted.

The space between the bore of the sleeve member 31 and the core 30 or where appropriate the cores of the cable 11 is filled with a two-part epoxy putty compound as indicated at 37. The compound 37 is chosen to adhere to the material of the sleeve member 31, this being preferably metal, and the bore surface 38 being preferably roughened to improve such adhesion. The compound 37 is also chosen for minimum shrinkage away from the core 30 or cores of the cable 11, on curing and while it is not necessary that the compound adheres to the cores of the cable, it is preferable that shrinkage is a minimum so that a close fit but not necessarily a sealed fit is achieved around the core or cores when the compound has cured.

In order to provide for a pressure-tight seal between the compound 37 and the core 30, or each core of the cable 11, a core seal 40 is positioned around each core of the cable adjacent the inner end of the sleeve member 31 before the compound 37 is put in place. Thus when the compound 37 cures the core seal 40 acts to provide a fluid-tight pressure seal between the compound 37 and the outer diameter of the respective core of the cable.

Thus it can be seen that a fluid-tight seal may be provided between the interior of an enclosure to which the gland body 1 2 is flitted, the gland body being sealed in the wall of the enclosure in conventional manner, and the outside of the enclosure. In particular the interior of the cable 11 is sealed from the interior of the enclosure so that in the event of any rise in pressure in the interior of the enclosure for instance as a result of an explosion, gases from the enclosure cannot enter the spaces between the cores in the cable 11 and the other parts of its structure to escape from the enclosure.

Thus it can be seen that the embodiment provides a gland which may be used as a flameproof gland or as a fluid pressure-tight gland for other purposes, or as a watertight gland.

Experience has shown that with conventional cable materials a gland as shown in Fig. 1 can withstand pressures of as much as a 1000 pounds per square inch without leakage over extended periods of time. The embodiment shown offers a performance in flameproof glands which far exceeds those peviously available.

The core seal 40 is preferably in the form of a piece of thin wall tubing folded back upon itself in the manner shown in Fig. 1 so that any fluid pressure in the enclosure to which the gland is fitted tends to open the seal 40 out to seal more firmly against both the cable core and the compound 37. The core seal 40 is preferably formed of neoprene or synthetic rubber material or other synthetic plastics material, the particular material being chosen being appropriate to the conditions to be resisted in use of the gland.

Figs. 6a through to 6v show various forms which the core seal may take. Those shown in Figs. 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6t, 6u and 6v function in a basically similar manner to that described with regard to the seal 40 in Fig. 1. The seals shown in Fig. 6c and 6g are operative in both directions with respect to the cable core and thus may resist pressures in the enclosure or outside the enclosure. The seals shown in Fig. 6e, 6f, 6t, 6u and 6v are formed with outward protuberances of various shapes to form a key into the compound 37 when it is cured.

The core seals shown in Figs. 6h, 6j, 61, 6m, 6n, 6p, 6q, 6r and 6s are basically sleeves of elastic material such as neoprene, synthetic rubber or synthetic plastics material arranged to form a seal between the compound and the cable core. Some of these such as that shown in Fig. 6j, 6r or 6s include outward protuberances to form a key in the compound 37, and some are provided with external wire clips indicated at 41 to grip the seals on the cable core and thus improve sealing between the core and seal. In some arrangements such as those shown at 6k and 6n, the effectiveness of the seal between the seal 40 and the cable core may be improved by an internal sealing ring such as an O-ring.

With the seals shown in Figs. 6h, 6j, 6k, 61, 6m, 6n, 6p, 6q, 6r, and 6s, it is preferable that the compound 37 is chosen such that it will also adhere to the material of the core seals 40 used.

Figs. 7a, 7b, 7c and 7d show various embodiments of the sleeve member 31 which may be used in the gland shown in Fig. 1. As can be seen Figs. 7a, 7b, and 7c show various sleeve members having means to enhance the grip between the compound 37 and the sleeve member 31 to better resist pressure arising inside or outside the enclosure tending to displace the compound 37 from the sleeve member. Fig. 7d shows a sleeve member without an external shoulder such as that shown at 36 in Fig. 1 and if this embodiment is used in Fig. 1 then the frictional grip of the seal 33 is utilised to prevent the sleeve member 31 moving in the gland body under pressure.

Fig. 2 shows a second gland embodying the invention which is generally similar to that shown in Fig. 1 and where similar parts are used and serve a similar purpose they have been given the same reference number and no further description will be given.

In this embodiment the core seal indicated generally at 50 provided around each cable core to be effective between the core and the compound 37 is formed in a different fashion. The core seal 50 comprises a layer of contact adhesive 51 applied around the surface of the cable core 30, a layer of metal tape such as aluminium tape half-lap wound around the adhesive 51 as indicated at 52 and then coated with an outer layer of contact adhesive as indicated at 53, the layers 51, 52 and 53 being put in place on the cable core before the compound 37 is placed in position. Preferably the metal tape is gripped on the cable core by means of a copper or other metal binding wire 54 wound round the metal tape with a few turns, three being shown, and having the ends twisted together to grip the metal tape onto the core.The binding wire 54 is chosen so that when the ends are twisted together and a break occurs the binding is tightened to the desired pressure around the cable core. The contact adhesive layers 51 and 53 are chosen to provide adhesion between the metal tape and the core and the metal tape and the compound 37 after curing respectively.

Fig. 3 shows a third cable gland embodying the invention which is again similar to that shown in Fig. 1 and again where parts are similar and/or serve the same purpose, they have been given the same reference numerals.

In this embodiment the core seal between each cable core and the compound 37 is in the form of a layer of low viscosity epoxy or other glue which will cure or set to form a layer indicated at 60 between the cable core and the compound 37. The glue layer 60 is preferably such that a bond may be formed between it and the compound 37 either during curing or setting or both, or after the layer 67 has cured or set.

Fig. 4 shows a further cable gland embodying the invention in which the gland body 12 is held in the wall of an enclosure by means of a circlip 70. Further the seal 33 is distorted to grip and seal against the sleeve member 31 by means of a screw-threaded ring 71. In other respects the gland of Fig. 4 is similar to that of Fig. 1.

Fig. 5 shows an arrangement embodying the invention in which the sleeve member 31 is itself located in an aperture in a wall of an enclosure by means of a screw-threaded ring 80. In other respects the arrangement of Fig. 5 is similar to that of Fig. 1.

Fig. 8 shows a yet further arrangement embodying the invention in which the sleeve member 31, in this case corresponding to that shown in Fig. 7d, is located and sealed in the gland body 1 2 by means of a metal olive 90 which is of known design per se and which is compressed in the gland body by means of a screw-threaded nut 91 to grip and seal against the sleeve member 31.

It is to be noted that in the arrangements of Figs. 4, 5 and 8 the outer sleeve of the cable 11 is not held in the gland.

Examples of materials which are suitable for the filling compound 37 in the above embodiments are: William Beared (CIBA GEIGY) - SP4424 Kompress - Kompound'E' Winn and Coales - Denso 2132/C Deacon - UW Cit - 664/K Plastic Padding Isopon However, other compounds may be used in accordance with the operating conditions expected in use of the arrangement.

Examples of contact adhesives which may be used for the layers 51 and 53 are: Ensis Compound - 356 Hylomar - PL32 Hellerman - HMT 100A Hellerman - WM 250 Devcon - Zip Patch Evo Stik - 528 Evo Stik - 873 Other suitable adhesives may however be used.

Claims (26)

1. An arrangement for sealing a cable core to a cable gland or other fitting, comprising a sleeve member arranged to be located and sealed in the cable gland or fitting with the cable core passing through the sleeve, a curable or hardenable compound filling disposed in the space around the core in the sleeve and sealed to the sleeve, and a core seal element disposed around the core to seal the core to the compound filling.

2. An arrangement for sealing a plurality of cable cores to a cable gland or other fitting, comprising a sleeve member arranged to be located and sealed in the cable gland or fitting with the cable cores passing through the sleeve, a curable or hardenable compound filling disposed in the space around the cores in the sleeve and sealed to the sleeve, and a respective core seal element disposed around each core to seal the core to the compound filling.

3. An arrangement as claimed in Claim 1 or 2, in which each said core seal element comprises an elastomeric tube.

4. An arrangement as claimed in Claim 3, in which said tube is folded back over itself to present a double edge to that side of the arrangement expected to experience a higher fluid pressure.

5. An arrangement as claimed in Claims 1, 2, 3 or 4, in which each said core seal element is formed of natural rubber.

6. An arrangement as claimed in Claims 1, 2, 3 or 4, in which each said core seal element is formed of synthetic rubber or neoprene.

7. An arrangement as claimed in Claims 1, 2, 3 or 4, in which each said core seal element is formed of synthetic plastics material.

8. An arrangement as claimed in any one of Claims 1, 2 or 3 in which said core seal element is substantially as herein described with reference to any one of Figs. 6a to 6v of the accompanying drawings.

9. An arrangement as claimed in Claims 1, 2 or 3 in which each said core seal element comprises a layer of low viscosity curable epoxy resin or hard setting glue.

10. An arrangement as claimed in Claims 1, 2 or 3 in which said core seal element comprises a layer of contact adhesive on the core, a second layer of wound metallic tape, and a third layer of contact adhesive.

11. An arrangement as claimed in Claim 10, in which said metallic tape is lap wound.

1 2. An arrangement as claimed in Claim 10 or 11, in which said metallic tape is tied to the core by means of an overwinding of metal wire.

1 3. An arrangement as claimed in any one of Claims 1 to 12, in which said sleeve member is roughened internally to assist bonding of said compound filling.

14. An arrangement as claimed in any one of Claims 1 to 12, in which said sleeve member is formed with ribs or grooves to assist bonding or gripping of said compound filling.

1 5. An arrangement as claimed in any one of Claims 1 to 14, in which said sleeve member is formed with an external shoulder to prevent axial movement thereof.

16. An arrangement as claimed in any one of Claims 1 to 12, in which said sleeve member is substantially as herein described with reference to any one of Figs. 7a to 7d of the accompanying drawings.

1 7. A cable gland including an arrangement as claimed in any preceding claim.

1 8. A cable gland as claimed in Claim 17, including a gland body having means to grip and seal to said sleeve member.

19. A cable gland as claimed in Claim 18, wherein a flame path is provided between said gland body and the sleeve member.

20. A cable gland as claimed in Claim 1 8 or 19, wherein a seal member is provided operative between the gland body and the sleeve member.

21. A cable gland as claimed in Claim 16, in which the seal member comprises a metal olive.

22. A cable gland as claimed in any one of Claims 18 to 21, in which said gland body includes means to seal against the external sleeve of a cable.

23. A cable gland as claimed in any one of Claims 1 8 to 22, in which said gland body includes means to grip armour wires of a cable.

24. A cable gland substantially as herein described with reference to any of Figs. 1, 2, 3, 4, 5 or 8 of the accompanying drawings.

25. A cable gland as claimed in Claim 20, including a core seal element or core seal elements substantially as herein described with reference to any one of Figs. 6a to 6v of the accompanying drawings.

26. A cable gland as claimed in Claim 20 or 21, including a sleeve member substantially as herein described with reference to any one of Figs. 7a to 7d of the accompanying drawings.